The Church of Jesus Christ and Latter-Day Saints is unquestionably a potent entity, with its own distinct moral code, culture, and customs that millions of people around the world follow. It adds on not only texts by Joseph Smith but an entire book (of Mormon) of its own upon the canonical Christian Scriptures- usually when a new religion such as Islam or Baha'i springs up there's a considerable amount of writings added. The Mormon Church sees itself as the true Christian church. Its theology and ideas is definitely distinct from the rest of Christendom.
So should Mormonism be considered the 4th Abrahamic religion? Or is it not different enough from Christianity? If an offshoot is different enough and big enough, shouldn't it be considered its own religion- after all, Islam is. Then again, there are more Jehovah's Witnesses than Mormons, and JW is already very different from mainstream Christianity, just as Mormonism is. Of course JW's don't add another book, they just use their own unique translation of the Bible.